Method of producing steel cylinder barrels having bonded bronze cylinder liners

ABSTRACT

The disclosure concerns a method for producing bronze lined cylinder bores in the steel cylinder barrel of a piston pump or motor. The liners are machined from bronze sleeves which are slip fitted into blind bores in a cylinder barrel blank, enveloped by sand, and then melted, bonded and re-solidified in a nonoxidizing atmosphere.

United States Patent- 151 3,707,035 1 51 Dec. 26,1972

Alger, Jr. et al.

[54] METHOD OFPRODUCING STEEL l0/l966 Leeming et al ..9l/499 353,716 5/l907 Monnotml ...l64/l l2 2,066,247 l2/l936 Brownback ..l64/80 BONDED BRONZE CYLINDER LINERS 3,025,596 3/1962 Ward et 31,"... ..29/474.4 x 72 Inventors; M -ti J M J N l H. 2,207,150 7/1940 Hirsch et al. ..l64/80 X Dunn, both of Watertown, N.Y. Przmary Examiner-John F. Campbell Asslgneei General Slgml Corporal"!!! Assistant ExaminerDonald C. Reiley, lll [22] Filed: No 27, 1970 1 Attorney-George Vande Sande, Harold S. Wynn &

. Jeffrey S. Medmck [2]] Appl. No.: 93,130

[57] ABSTRACT v [52] U.S. Cl. .29/527.6, 29/4733, 92/169, The disclosure concerns a method for producing 164/76 164/112 bronze lined eylinder bores in the steel cylinder barrel [Sl] ll'lt. Cl. ..B23l( 19/00 of a piston pump or motor. The nets are machined [581 of Search-"29,4733,474-3'474-4 from bronze sleeves which are slip fitted into blind 29/DIG- 8; 112; 92/169 bores in a cylinder barrel blank, enveloped by sand,

I and then melted, bonded and re-solidified in a non-ox- References Clled idizing atmosphere.

3,l69,488 2/1965 (iallig er "92 57 [3 I9 22 2] 1 \\IUR\\\/QQ\\\\ Q 4* E"; Q

A Q Q z-- 12 ::E\ NH 1 METHOD OF PRODUCING STEEL CYLINDER BARRELS HAVING BONDED BRONZE CYLINDER LINERS BACKGROUND AND SUMMARY OF THE INVENTION In hydraulic pumps and motors of the rotary cylinder barrel, longitudinally reciprocating piston type, the

pistons are moved on their discharge strokes by an 1 by using bronze cylinder bore liners; however, since, in.

the usual case, the inner end of each liner is subjected to the pressure within the cylinder bore, the interfaces between the liners and the bore walls provide potential leakage paths along which fluid may escape. Although considerable effort has been directed toward creating a reliable fluid-tight bond between the bronze liner and the steel bore wall, as far as we are aware none of these .prior attempts has been entirely satisfactory.

In one prior design, see US. Pat. No. 3,169,488, granted Feb. 16, 1965, the need for a fluid-tight bond between the liner and the bore wall is eliminated by extending the liner completely through the cylinder barrel. This scheme, however, inherently reduces the amount of steel around the bores at the high pressure end of the cylinder barrel, and cannot be used in todays high performance units which operate continuously at pressures of 5,000 p.s.i. and at rotary speeds around 4,000 rpm. Furthermore, since the liners in the patented design are machined from solid bronze rods, that approach wastes considerable amounts of this expensive bearing material.

The object of this invention is to provide a method of lining cylinder bores which affords the good metallurgical bond between the bronze and steel required for leakage-free operation. According to the invention, the liners are formed in situ from preformed bronze sleeves which are slip fitted into blind bores drilled in a steel cylinder barre] blank. The sleeves are enveloped by sand masses which fill the voids within the bores, and the barrel bIank-sleeve-sand assembly is then heated to a temperature between about l,900 and 2,000F in a non-oxidizing atmosphere to melt the bronze and effect an intimate bond between this metal and the steel. Thereafter, the assembly is cooled in the controlled atmosphere to resolidify the bronze, and then air cooled to room temperature. Finally, the sand masses are removed, the barrel blank is machined to remove the end regions of the re-solidified sleeves where shrinkage may have occurred, and the final cylinder bores are machined in the bronze sleeves. The process creates a reliable mechanical, as well as a metallurgical, bond between each sleeve and the steel of the blank, so it eliminates the interface leakage difficulties experienced with prior lining techniques. And, since formation of the finished cylinder bores requires removal of only a small amount of the relatively expensive bronze material, the process is economical.

BRIEF 7 DESCRIPTION OF THE DRAWING The preferred embodiment of the invention is described herein in detail with reference to the accompanying drawing in which:

, FIG. 1 is a top plan view of the cylinder barrel blank. FIG. 2 is a sectional view taken on line 22 of FIG.

FIGS. 3 and 4 are sectional views similar to FIG. 2

() depicting various stages of the process.

FIG. 5 is an axial sectional view of the finished cylinder barrel.

FIG. 6 is a plan view showing the valving face of the cylinder barrel ofFIG. s. I

DESCRIPTION OF PREFERRED EMBODIMENT The initial step of the preferred process consists in fabricating the cylinder barrel blank 11 shown in FIGS. 1 and 2. The blank is made of a suitable steel, such as SAE 52100, 1045 or 4150, and is drilled to provide a through axial bore 12 and a circular series of parallel,

'blind bores 13. The bores 13 are left in the rough drilled state since surface irregularities aid, rather than hinder, the bonding process. Moreover it has been found that the process is not adversely affected by the formation of rust on the walls of bores 13. After rough machining, blank 11 is cleaned to remove chipsand then vapor degreased. Degreasing is not essential because any adherent oil or grease film will be burned off before the bronze-steel bond is effected. However, since these volatiles may leave a residue on the bore walls which could cause localized impairment of the bond, it is considered best to remove them initially.

Following these initial steps, a bronze sleeve 14 having a wall thickness on the order of 0.16 inch is inserted into each bore 13 (see FIG. 3). The sleeves 14 form a slip fit with the bores, i.e., there is a ,diametral clearance on the order of 0.001 to 0.002 inches. between these parts, and each is mechanically deformed so that its end portions engage the steel blank 11 tightly enough to preclude entry of sand into the clearance space. This deformation is effected by a tapered mandrel 15 which is pressed downward against the inner peripheral edge at the top end of the sleeve. The action of the mandrel expands the upper end of sleeve 14 to produce the required sea] at outer peripheral edge 16, and also forces sleeve 14 downward against drill point 17 to effect a sand-excluding seal at outer peripheral edge 18. Sleeves 14 can be made of various bronzes, but experience indicates that the composition should be free of zinc and nickel because these metals separate out and form a brittle interface which may crack under the service conditions encountered by the finished cylinder barrel. The composition should also have a lead content as low as possible because this metal will bleed out during the heat treatment of the driving splines of the cylinder barrel. Bronzes having the following composition by weight have proven acceptable:

a. percent copper, 10 percent tin, 10 percent lead b. 89 percent copper, l 1 percent tin c. 90 percent copper, 10 percent tin However, the preferred sleeve 14 is made of a bronze containing percent copper, 10 percent tin and 5 percent lead. This material is obtained commercially in charging each bore 13 with a mass of sand 19 so as to form an envelope for the bronze sleeve 14. The sand need not be rammed in place, but it is advisable to vibrate the blank 11 as the sand is introduced in order to insure that all voids are filled. Each sand mass 19 must fill the void in the bore below the-level of the upper end of sleeve 14, and it must be prevented from floating on themolten bronze when the sleeve 14 is subsequently meltedfThe most convenient way to accomplish this is to fill the entire space within bore 1 3 with sand which is struck off flush with the upper end face 21 of blank 1 l, and to rest on face 21 a plate 22 of sufficient weight to resist upward movement of the sand masses. Plate 22, which is made of cast iron, also serves as a hot top which controls the rate of cooling of the sleeves 14 during a later stage of the process. The sand masses 19 may be composed of regular dry casting sand, but preferably a core sand isemployed because it compacts better and is less likely to be jostled out of the bores 13 during handling of the sand-filled blank.

After the blank-sleeve-sand assembly 23has been completed, the .hot'top 22 is applied and the unit is placed in a furnace and supported in the upright position illustrated in FIG. 4. The furnace should contain a non-oxidizing atmosphere, such as the filtered natural gas product commonly employed to control decarbu-- rization of the steel in blank 11 during heat treatment, and, in a typical case, it would be at a temperature of about l,600F at the time assembly 23 is introduced. Furnace temperature is then increased to an elevated level above the melting range of the bronze and held there long enough to insure that all parts of assembly 23 reach a temperature which will produce a good metallurgical bond between the bronze and the steel. Although bonding can be effected at an assembly temperature on the order of 1,900F, experience indicates that a temperature of 1,950F is needed in order to provide the degree .of bonding reliabilityrequired for a production process. The furnace temperature and length of time this temperature must be maintained in order to achieve the required assembly temperature must be determined empirically because these factors vary with furnace design and loading, i.e., the number of assemblies 23 being heated. The final selection involves a compromise since higher temperatures shorten holding time but also cause excessive evaporation of bronze and, because of localized hot spots, involve some risk of melting portions of steel blank 1 1. Our studies show-that furnace temperatures above 2,000F are too risky and are not actually demanded by practical production considerations. For example, using a standard heat treating furnace capable of simultaneously processing 30 assemblies, we found that acceptable bonds were produced reliably at a furnace temperature of l ,990F which was maintained for 1 hour.

During the heating cycle just mentioned, the bronze sleeves 14 melt, and a small portion of this metal does migrate downward and coat the surfaces of the drill points 17. This effect is not detrimental'and is significant only tothe extent that it highlights the necessity for making bores 13 blind at their lower ends. The bronze, however, does not infiltrate the sa'nd masses 19. This characteristic is of vital importance because it insures that the bronze remains in contact with the steel around the entire circumference of bore 13 and throughout the length required for the final liner. As a result, a good bond will be created over the entire interface between the bronze and the steel.

At the end of the heating cycle, i.e.,.after all parts of assembly 23 have reached the selected bonding temperature, the furnace is allowed to cool so that the temperature of assembly 23 reduces below the melting range of the bronze. Typically, this phase of the process consumes about one hour, furnace temperature decreases to about l,400F, and the temperature of assembly 23 drops to a level below 1',500F. These conditions insure solidification of the bronze and permit opening of the furnace without risk of explosion of the controlled atmosphere. Assembly 23 is now removed from the furnace and allowed to air cool to room temperature.

The upper ends of bronze sleeve 14 tend to solidify and cool more rapidly than the lower ends which are completely encased in the steel blank. This condition is undesirable because it could result in the formation of shrinkage cracks at the upper ends of the sleeves, or in the creation of voids at some lower level. In the illustrated embodiment, the risk that these adverse effects will be encountered is minimized by the hot top 22 which tends to make uniform the rate at which each sleeve solidifies and cools. As a result, any shrinkage will occur at the upper ends of the sleeves in regions which are machined away during final finishing of the cylinder barrel.

While the core sand masses 19 remain intact as long as assembly 23 is in the non-oxidizingatmosphere, they crumble shortly after being subjected to air. Thus, after assembly 23 air cools sufficiently to be handled, most of the sand can be removed easily by turning the assembly upside down. Blank 11 is now sand blasted and then transformed into the finished cylinder barrel shown in F IGS. 5 and 6. The finishing steps include:

1. Machining the inner and outer peripheral surfaces 24 and 25, respectively, and the front face 26.

2. Cutting and heat treating driving splines 27. I

3. Machining a run-out chamber 28 in, and an arcuate port 29 for, each cylinder bore.

4. Boring and honing the cylinder bores 31.

5 Grinding and lapping valving face 32.

It should be noted that the upper ends of the resolidified sleeves 14 are removed during the machining of front face 26. Because of this, any shrinkage occurring during resolidification will not have a detrimental effect upon the bronze liners of the finishedcylinder barrel.

Although the foregoing description treats only the process steps of the present invention, it should be understood that, in the complete commercial process, bonding of the cylinder bore liners is effected simultaneously with the valve plate bonding step of our application Ser. No. 93,129, or Ser. No. 93,297, both filed concurrently herewith.

We claim:

1. A process for making bronze-lined cylinder bores in a cylinder barrel for a piston pump or motor comprising the steps of fabricating a steel barrel blank (11) having an end face (21) and containing a circular series of blind bores (13) which open through said face;

slip fitting a bronze sleeve (14) into each bore deforming the ends of each sleeve (14) into engagement with cooperating portions of the steel blank to create joints which preclude'entry of sand particles into the clearance space between the sleeve (14) and the wall of the bore (13);

. orienting the blank (11) in an upright position with said end face (21) pointing up and completely filling with a mass of sand (19) the void within each bore (13) at least below the level of the upper end of the sleeve (14);

. supporting the blank-sleeve-sand assembly (23) in said upright position while heating it in a non-oxidizing atmosphere to a temperature between l,900 and 2,000F to thereby melt the sleeves (14) and cause the bronze to bond with the steel walls of the bores (13);

. maintaining a downward pressure on the sand masses (19) throughout the period in which the bronze is molten to thereby prevent flotation of said masses;

. cooling said upright assembly (23) in the presence of the non-oxidizing atmosphere to re-solidify the bronze;

. further cooling the assembly (23) to room temperature;

. removing the sand masses (19) from the bores finish machining said end face (21) of the barrel blank (11) so as to remove the upper end portion of each re-solidified sleeve; and

finish machining a piston-receiving cylinder bore (31) in each re-solidified sleeve.

The process defined in claim 1 in which said sand is a core sand.

3. The process defined in claim 1 in which the assembly (23) is heated to a temperature of l ,950F.

4. The process defined in claim l-in which a. the sleeves (14) are made of a bronze containing, by weight, percent copper, 10 percent tin, and 5 percent lead; and

b. the barrel blank (11) is made of SAE 52l00, SAE

1045 or SAE 4l50 steel.

5. The process defined in claim 4 in which the bronze is nickel-free.

6. The process defined in claim 1 in which a. each bore (13) is filled to the top with sand; and

' b. the blank-sleeve-sand assembly (23) is provided cent tin and 5 percent lead; b. the barrel blank (11) 18 made of SAE 52100, SAE

1045 or SAE 4150 steel;

c. said sand is a core sand;

d. the assembly (23) is heated to a temperature of e. the bores 13) are filled to the top with sand;

f. the assembly (23) is provided with an iron hot top (22) which rests on said end face (21) and holds the sand masses (19) against flotation;

g. the assembly (23) is cooled in the non-oxidizing atmosphere to a temperature between l,400 and l,500F; and h. said further cooling is effected in air.

mum NM. 

2. The process defined in claim 1 in which said sand is a core sand.
 3. The process defined in claim 1 in which the assembly (23) is heated to a temperature of 1,950*F.
 4. The process defined in claim 1 in which a. the sleeves (14) are made of a bronze containing, by weight, 85 percent copper, 10 percent tin, and 5 percent lead; and b. the barrel blank (11) is made of SAE 52100, SAE 1045 or SAE 4150 steel.
 5. The process defined in claim 4 in which the bronze is nickel-free.
 6. The process defined in claim 1 in which a. each bore (13) is filled to the top with sand; and b. the blank-sleeve-sand assembly (23) is provided with an iron plate (22) which rests on said end face (21) and serves to prevent flotation of said sand masses (19) and to control the rate of cooling of the bronze.
 7. The process defined in claim 1 in which a. the assembly (23) is cooled in the non-oxidizing atmosphere to a temperature between 1,400* and 1,500*F; and b. said further cooling is effected in air.
 8. The process defined in claim 1 in which a. the sleeves (14) are made of a nickel-free bronze containing, by weight, 85 percent copper, 10 percent tin and 5 percent lead; b. the barrel blank (11) is made of SAE 52100, SAE 1045 or SAE 4150 steel; c. said sand is a core sand; d. the assembly (23) is heated to a temperature of 1,950*F; e. the bores (13) are filled to the top with sand; f. the assembly (23) is provided with an iron hot top (22) which rests on said end face (21) and holds the sand masses (19) against flotation; g. the assembly (23) is cooled in the non-oxidizing atmosphere to a temperature between 1,400* and 1,500*F; and h. said further cooling is effected in air. 